Bag filter



Ma'lrch 26, 1935. R. B. RATHBUN BAG FILTER Filed July 9, 1932 2 Sheets-Sheet 2 INVENTOR Kass Buxiazz ZIa/kum @154 6 ATTORNEY Patented Mar. 26, 1935 UNI-TED STATES PATENT V OFFICE BAG FILTER Application July 9, 1932, Serial No. 621,552

10 Claims.

The invention relates to the separation of solids from fiuids in which they are suspended, and more particularly to filter bags for removing fume, such as are used in connection with the smelting and refining of metals.

According to one form of practicing the invention, the bag may comprise a stiif framework to which a filter mat may be suitably secured. The filter mat may conveniently be made by weaving strips of steel wool and lengths of wire to form a fabric. This fabric may be passed between suitable rolls to flatten it out and close the interstices.

If desired, an expansion joint may be provided, located preferably between the bag and the lower partition under which the gas to be filtered is fed. This prevents the bag from getting out of shape due to expansion and contraction.

For removing the fume deposited on the inside of the bag a suction device may be provided. This suction device may comprise a plurality of suction heads or nozzles secured to a central vertical conduit to which suction pressure is applied. It is desirable that the suction heads have wide lips at the mouths thereof to prevent leakage at this point. A convenient way to widen the lip of the nozzle is to provide flanges secured to the nozzles.

In order to keep the suction pressure to the desired degree throughout the length of the suction apparatus, the size of the slots in the suction heads may vary either gradually or in steps, being narrowest at the point at which the suction is applied and becoming increasingly wider as the distance from this point is increased.

The invention also consists in certain new and original features of construction and combination of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. 1 illustrates the construction of a bag according to the invention;

Fig. 2 is a plan view of the top of the bag;

Fig. 3 is a detail of the apparatus on the top of one of the bags;

Fig. 4 isa further detail of the upper part of one of the bags;

Fig. 5 is an enlarged view illustrating the construction of the bag and associated apparatus;

Fig. 6 is a section on the line 6-6 of Fig. 5;

Fig. 7 is a. detail of one of the suction nozzles taken on the line 7-7 of Fig. 1;

Fig. 8 is a similar section taken on the line 8-8 of Fig. 1; and

Figs. 9 and 10 are details of the filter mat.

In the following description and in the claims, various detailswill be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Like reference characters denote like parts in the several figures of the drawings.

In the drawings accompanying and forming part of' this specification, certain specific disclosure of the invention is made for purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

Referring now to the drawings, the bag 23 is supported by the top wall 42 of the building, as indicated particularly in Figs. 1, 4 and 5. The bag is provided with a flanged collar 43 which rests upon the top wall 42 and which cooperates with a seal 142 which may be made up principally of steel wool.

The bag is made up of a plurality of stiff rods 45 suitably welded or otherwise secured to the top ring 43 and passing through holesin a plurality of fiat rings 44, as illustrated. The rods 45 are suitably secured to a lower ring 46 at their lower ends.

Since the bag is supported at the top by a gas tight joint, provision is made at the bottom for expansion of the bag. The lower part of the bag has an angular ring 4'? connected to the ring 46 and a cylindrical sleeve 48 connected to the ring 47. The sleeve 48 is adapted to slide within a seal 50 of steel wool or other suitable material contained in a holder 51 and mounted upon the partition 123.

It will be understood that the stiff wire rods 45 and flat rings 44 are sufiiciently close together to provide a stiff rigid assembly to support a filter mat 52 in accurate fixed position. This filter mat is illustrated in Figs. 9 and 10 and may be made as follows It may be made up in the form of a cloth or fabric comprising a warp of, for example, #20 copper wire, indicated by 53, and awoof of the strands of steel wool, indicated by 54.

Steel wool in ribbon form is available on the market in strips four inches wide and about oneinch in diameter.

quarter inch thick (unpressed) of any length desired, with the fibres running substantially parallel.

According to the invention these strips are cut or pulled into strips one-half the original width and rolled into strands about three-eighths of an These strands form the woof of the fabric, as above described. and may be woven, by hand or otherwise, with the warp wires 53 into a mat. The warp wires may be spaced about three-quarters of an inch apart and stretched between nails driven into a board, if desired, and the woof strands woven over and under in a manner well known in the art of weaving.

When the weaving is finished, the mat may be passed through tinners rolls several times, which closes all the small interstices and covers the warp wires 53 with a smooth surface of steel wool, the mat then taking the appearance somewhat as indicated in Fig. 10.

This mat is secured to the inside surface of the cylinder made up of the rods 45 by suitable attachment, such as, by fine wire loops at sufficiently close points to properly support the mat. It is better to mount the mat so that the rotary suction nozzles move parallel to the strands of steel wool to prevent roughing up the mat, although satisfactory results have been obtained with the nozzle moving parallel to the warp wires.

As illustrated in Figs. 1 and 5, the central supporting nozzle stem 28 may be made up of sections, the lower end being closed and supported in a suitable bearing 55 which in turn is supported by radial rods extending through the adjacent walls of the bag.

At the top of the bag, the stem 28 passes through a plate 59 having a suitable seal 60 (Fig. 4). The plate 59 rests upon a collar 56 which in turn rests upon a plate 57 secured to the collar 43.

Keyed to the rotary stem 28 is a worm wheel 62 which rests upon a thrust bearing 61. Driving the worm wheel 62 is a worm 70 which in turn is driven by gears 69 driven by a motor 68.

Mounted upon the plate 59 is a bracket 64 which supports a stationary pipe 65 to which is secured the stationary element 165 of a slip joint, the other part of which is secured to the stem 28. The stationary pipe 65 is provided with a detachable connection 66 with branch pipe 67 secured to the main suction pipe for a reason explained below.

Also mounted on the bracket 64 is the solenoid 38 which operates the damper 37 in the pipe 65, closing off the suction to the suction head of the particular bag.

Thus it will be seen that by disconnecting the connection 66, the entire bag 23 and all associated apparatus may be lifted clear out of the bag compartment by a crane (not shown).

Secured to the central rotary stem 28 are a plurality of separate suction nozzles 27. Each nozzle 27 is made up of a cylindrical tube 71 having its ends closed and provided with a longitudinal slot 74. Secured to the edges of this slot 74 are a pair of wide ears or flanges 75 to prevent the suction nozzle from digging into the filter mat and to cut down suction leakage at this point.

Each cylindrical tube 71 is supported by an upper branch 171 and a lower branch 76, each of which is swiveled on corresponding branches 72 and 73 respectively. Each lower branch 76 may creased.

be provided with a lever 77 to which is connected a flexible strand 78 having a weight 79 and paning over branch 73 in such manner as to yieldably hold the suction nozzle 27 against the wall of the bag.

It will be noted particularly from Fig. 1 that the suction nozzles are oppositely mounted and that each nozzle bears against a pair of flat rings 44 at its ends, these rings operating as tracks for the nozzles to prevent the nozzles from digging into the mat.

In operation it will be understood that the fume laden gas is supplied by a suitable blower from the metallurgical process or other source and is directed under the partition 123, the gas passing up into the bag through the filter mat to the space outside of the bag where it is collected and sent to waste or any other desired point.

The fume deposits on the inside surface of the bag and is removed by the rotating nozzles 27. The relatively concentrated mixture of gas and fume obtained from the nozzles may be separated in centrifugal dust collectors (not shown).

For repairs, it is only necessary to disconnect the apparatus from the main suction pipe 67 by the coupling 66 and the entire bag assembly may be raised by a suitable crane overhead (not shown), the expansion joint at 51 permitting displacement of the bag at this point.

It will be understood that for effective cleaning actual contact must be made between the edges or lips of the suction nozzles and the filter mat. No wire or screen must be interposed since in this case air would leak in through the spaces in the mesh of the screen.

Sufiicient pressure must be applied to the nozzle against the surface of the filter mat to effect a seal, but not enough to cause undue wear. It is obvious that this pressure must be kept constant and the weights 79 perform this function very advantageously, being unaffected by differences in temperature.

Furthermore, the surface of the filter mat must be kept absolutely even and free from depressions or else the suction will be destroyed sufficiently to prevent cleaning. The stiff wire framework of the present bag holds the filter mat in such proper position and holds it in a true circle over its entire length and at the same time support is obtained without destroying any of the filtering area of the mat.

The provision of the tracks 44 on which the nozzles ride and the provision of the fianges 75 insure close contact between the nozzles and the filter mat and yet prevent undue wear and digging in.

The total slot area in the suction heads must be kept as low as practical without cloggging up, to maintain sufficient suction pressure. By keeping the suction slots as narrow as possible and having only a single filter nozzle at each position, a filter head of maximum effective length is obtained.

In order to maintain a sufficiently even suction pressure throughout the entire extent of the suction head, the suction slots are made narrower at the top where suction is applied than at the bottom of the bag. A narrow slot is advantageous to obtain maximum velocity, since it is velocity which does the cleaning.

It is important to have the nozzle speed of cleaning correct. If the speed is too great, the areaofpoorfilteringbehindthenozzleisinly through it by the suction nozzles. It is obvious that the cleaning operation may take place while normal filtering operation is being carried on, orthe normal filtering through the bag may be stopped while vacuum cleaning is done.

While certain novel features of the invention have been disclosed and are pointed out inthe annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In a bag, a substantially cylindrical, substantially rigid framework made up of circular rings and stiff longitudinal rods, 9. filter mat secured to said framework on the inside of the bag, said rings projecting inwardly between portions of said filter mat and providing tracks, and cleaning apparatus for said filter mat guided by said tracks. v 1

2. In a bag, a substantially cylindrical, substantially rigid framework comprising fiat circular rings, each ring having a plurality of holes, stiff longitudinal rods passing through said holes, a filter mat secured to said rods on the inside of the bag, said rings projecting between portions of said filter mat and providing tracks, and cleaning apparatus for said filter mat guided by said tracks.

3. In a filtering system, a filter mat, a cleaning head adapted to pass over said mat, said cleaning head having a cleaning aperture and rigid wide lips on the sides of said aperture, said lips having direct contact with said filter mat over substantially the entire extent from said aperture to the free edges of said lips to cut down fluid leakage at the edges of said aperture.

4. In a filtering system, a filter mat having a matted fibrous surface, a cleaning head adapted to pass over said mat, said cleaning head having a substantially-long and narrow slot and rigid wide flanged lips on the sides of said slot, said lips having direct contact with said matted fibrous surface over substantially the entire extent from said slot to the free edges of said lips to cut down fiuid leakage and to prevent digging in the filter mat.

5. In a filter apparatus, a filter medium comprising a supporting, open mesh framework, a filter mat secured thereto, the area of said framework in contact with said mat being -substantially negligible as compared to the total area of the mat to subject as great a part of the filter mat as possible to maximum action, means for passing the fluid to be cleaned through said filter medium, a cleaning head, means for moving said cleaning head and filter medium relatively to remove the deposited particles therefrom, and means for passing fluid through said head.

6. In a filtering system, a filter medium comprising an open mesh framework, a filter mat comprising a woven fabric of wires interwoven comprising an open mesh supporting framework,

a filter mat secured thereto, the openings in said framework being great compared to the thickness of structural members thereof to expose as great a part 'of the filter mat as possible to cleaning action, said filter mat comprising a woven fabric of parallel wires interwoven with strands of fibrous material, said fabric having been compressed to close the interstices thereof, means for passing the fiuid to be cleaned through said filter medium, a suction head, means for moving said cleaning head and filter medium relatively to remove the deposited particles therefrom, and means for applying suction to said suction head. I

8. In a gas filtering system, a filter medium comprising a woven fabricof parallel wires interwoven with strands of fibrous material, said fabric being compressed to close the interstices thereof, means to pass a particle-laden gas through said filter medium in one direction and means to pass a cleaning gas through said filter medium in the opposite direction to remove the deposited particles.

9. In a filtering system, a filter medium comprising a woven fabric of parallel wires interwoven with strands of fibrous material, means for passing the fiuid to be cleaned through said filter medium, a cleaning head, means for passing fiuid through said cleaning head and means to move said cleaning head and filter medium relatively over the surface of said filter medium to remove locally the deposited material.

10. In a filter apparatus, a filter comprising a cylindrical, rigid framework made up of circular rings and stiff longitudinal rods, a filter mat secured thereto, the openings in said frame: work being much greater than the cross sections of said rings and rods, means for passing the fluid to be cleaned through said filter, a cleaning head, means for moving said cleaning head and filter medium relatively over the surface of the filter medium to remove the deposited particles therefrom, and means for producing a fluid current between said cleaning head and filter mat.

ROSS BUXfION RATHBUN. 

